A pretty hearty developer list has surfaced from Japan regarding NGC development. It's looking good!
According to Japanese website 64 World, and translated by The Nintendo Project, the follwing list of Japanese third-party developers are said to have either requested or are in possesion of Gamecube development kits:
Konami
Kemco
Koei
Namco
Hudson
Media Factory
Atlus
Epoch
This list basically consists of some very key Japanese developers and will help furthar establish the Gamecube as the "ultimate games machine". The website then reiterated the fact that Capcom, Mobile 21 and Rareware were also creating games for Gamecube.